1. Field of the Invention
The present invention relates generally to a satellite receiver system and in particular, to a system architecture for control and data signal distribution on coaxial cable.
2. Description of the Related Art
Satellite broadcasting of communications signals has become commonplace. Satellite distribution of commercial signals for use in television programming currently utilizes multiple feedhorns on a single Outdoor Unit (ODU) which supply signals to up to eight IRDs on separate cables from a multiswitch.
FIG. 1A illustrates a typical satellite television installation of the related art.
System 100 uses signals sent from Satellite A (SatA) 102, Satellite B (SatB) 104, and Satellite C (SatC) 106 that are directly broadcast to an Outdoor Unit (ODU) 108 that is typically attached to the outside of a house 110. ODU 108 receives these signals and sends the received signals to IRD 112, which decodes the signals and separates the signals into viewer channels, which are then passed to television 114 for viewing by a user. There can be more than one satellite transmitting from each orbital location.
Satellite uplink signals 116 are transmitted by one or more uplink facilities 118 to the satellites 102-104 that are typically in geosynchronous orbit. Satellites 102-106 amplify and rebroadcast the uplink signals 116, through transponders located on the satellite, as downlink signals 120. Depending on the satellite 102-106 antenna pattern, the downlink signals 120 are directed towards geographic areas for reception by the ODU 108.
Each satellite 102-106 broadcasts downlink signals 120 in typically thirty-two (32) different frequencies, which are licensed to various users for broadcasting of programming, which can be audio, video, or data signals, or any combination. These signals are typically located in the Ku-band of frequencies, i.e., 11-18 GHz.
Future satellites will likely broadcast in the Ka-band of frequencies, i.e., 18-40 GHz, but typically 20-30 GHz. For example, satellite 122 is at 99 degrees, satellite 124 is at 103 degrees, satellite 126 is at 95 degrees, and satellite 128 is at 72.5 degrees. Satellites 122 and 124 are typically Ka-band satellites; however, other orbital slots can be used at Ka-band without departing from the scope of the present invention. Satellite 128 at 72.5 degrees is typically used for local programming, via spot beams that serve different geographic areas through frequency reuse and/or geographic diversity to allow the antenna beams to service different geographical areas.
FIG. 1B illustrates a multiple dwelling unit in a typical urban setting.
Multiple dwelling unit (MDU) 130 is adjacent to MDU 132 and diagonally opposed to MDU 134. A given dwelling unit 136 in MDU 130 is shown for illustrative purposes. If satellite signals 120 are arriving from direction 138, then dwelling unit 130 can mount an ODU 108 facing direction 138 and potentially receive satellite signals 120. However, the majority of the dwelling units in MDU 132 and 134 will not have clear access to direction 138, and, as such, will not have access to satellite signals 120. Further, if satellite signals 120 are incident from direction 140, then dwelling unit 136 will not have access to satellite signals 120. This problem also affects off-air television signals; an antenna for dwelling unit 136 will be shadowed by not only MDU's 132 and 134, but by MDU 130 depending on where the off-air signal transmitter is located with respect to MDU 130 and dwelling unit 132. In essence, even if dwelling unit 136 has a complete view of the southern sky, other dwelling units in MDU 130 will not, which will eliminate or seriously degrade the reception and use of satellite signals 120 in those units.
FIG. 2 illustrates a typical ODU of the related art.
ODU 108 typically uses reflector dish 222 and feedhorn assembly 224 to receive and direct downlink signals 120 onto feedhorn assembly 224. Reflector dish 222 and feedhorn assembly 224 are typically mounted on bracket 226 and attached to a structure for stable mounting. Feedhorn assembly 224 typically comprises one or more Low Noise Block converters 228, which are connected via wires or coaxial cables to a multiswitch, which can be located within feedhorn assembly 124, elsewhere on the ODU 108, or within house 110. LNBs typically downconvert the FSS-band, Ku-band, and Ka-band downlink signals 120 into frequencies that are easily transmitted by wire or cable, which are typically in the L-band of frequencies, which typically ranges from 950 MHz to 2150 MHz. This downconversion makes it possible to distribute the signals within a home using standard coaxial cables.
The multiswitch enables system 100 to selectively switch the signals from SatA 102, SatB 104, and SatC 106, and deliver these signals via cables 224 to each of the IRDs 112A-D located within house 110. Typically, the multiswitch is a five-input, four-output (5×4) multiswitch, where two inputs to the multiswitch are from SatA 102, one input to the multiswitch is from SatB 104, and one input to the multiswitch is a combined input from SatB 104 and SatC 106. There can be other inputs for other purposes, e.g., off-air or other antenna inputs, without departing from the scope of the present invention. The multiswitch can be other sizes, such as a 6×8 multiswitch, if desired. SatB 104 typically delivers local programming to specified geographic areas, but can also deliver other programming as desired.
To maximize the available bandwidth in the Ku-band of downlink signals 120, each broadcast frequency is further divided into polarizations. Each LNB 228 can only receive one polarization at time, so by aligning polarizations between the downlink polarization and the LNB 228 polarization, downlink signals 120 can be selectively filtered out from travelling through the system 100 to each IRD 112A-D.
IRD's 112A-D currently use a one-way communications system to control the multiswitch. Each IRD 112A-D has a dedicated cable 224 connected directly to the multiswitch, and each IRD independently places a voltage and signal combination on the dedicated cable to program the multiswitch. For example, IRD 112A may wish to view a signal that is provided by SatA 102. To receive that signal, IRD 112A sends a voltage/tone signal on the dedicated cable back to the multiswitch, and the multiswitch delivers the SatA 102 signal to IRD 112A on dedicated cable 124. IRD 112B independently controls the output port that IRD 112B is coupled to, and thus may deliver a different voltage/tone signal to the multiswitch. The voltage/tone signal typically comprises a 13 Volts DC (VDC) or 18VDC signal, with or without a 22 kHz tone superimposed on the DC signal. 13VDC without the 22 kHz tone would select one port; 13VDC with the 22 kHz tone would select another port of the multiswitch, etc. There can also be a modulated tone, typically a 22 kHz tone, where the modulation schema can select one of any number of inputs based on the modulation scheme.
To reduce the cost of the ODU 108, outputs of the Ka-band LNBs 128 present in the ODU 108 can be combined, or “stacked,” depending on the ODU 108 design. The stacking of the LNB 228 outputs occurs after the LNB has received and downconverted the input signal. This allows for multiple polarizations, one from each satellite 102-106, to pass through each LNB 228. So one LNB 228 can, for example, receive the Left Hand Circular Polarization (LHCP) signals from SatC 102 and SatB 104, while another LNB receives the Right Hand Circular Polarization (RHCP) signals from SatB 104, which allows for fewer wires or cables between the LNBs 228 and the multiswitch.
The Ka-band of downlink signals 120 will be further divided into two bands, an upper band of frequencies called the “A” band and a lower band of frequencies called the “B” band. Once satellites are deployed within system 100 to broadcast these frequencies, each LNB 228 can deliver the signals from the Ku-band, the A band Ka-band, and the B band Ka-band signals for a given polarization to the multiswitch. However, current IRD 112 and system 100 designs cannot tune across this entire frequency band, which limits the usefulness of this stacking feature.
By stacking the LNB 228 inputs as described above, each LNB 228 typically delivers 48 transponders of information to the multiswitch, but some LNBs 228 can deliver more or less in blocks of various size. The multiswitch allows each output of the multiswitch to receive every LNB 228 signal (which is an input to the multiswitch) without filtering or modifying that information, which allows for each IRD 112 to receive more data. However, as mentioned above, current IRDs 112 cannot use the information in some of the proposed frequencies used for downlink signals 120, thus rendering useless the information transmitted in those downlink signals 120.
Further, the installation described above is designed for installation in a single residence, rather than in an apartment building or other large structure. Multiple Dwelling Units (MDUs), e.g., an apartment building, hotel, etc., for some configurations may be able to have their own ODU 108; however, many MDUs may not be able to have an ODU 108 installed for each unit. For example, an apartment building may not be able to have an ODU 108 installed for some apartments because the ODU 108 cannot be properly pointed at satellites 102-106. Hotels may also not be able to install ODUs 108 for every room, for pointing and/or billing reasons.
It can be seen, then, that there is a need in the art for a satellite broadcast system that can be expanded to include MDUs.